The present invention relates to an image erecting and beam path interchanging optical system for use with a stereo microscope, such as a slit-lamp biomicroscope or operating microscope, for use during diagnostic observation, laser treatment or vitreoretinal surgery. More particularly the invention relates to a reflection based image erecting system, utilizing mirrors, prisms, or a combination of both to achieve both the vertical and horizontal inversion required in producing an upright and correctly oriented image, which can be retrofitted to an existing microscope, either as an external attachment to the end of the microscope containing the main collection lens or as a removable component positioned within the stereo microscope, between the end of the microscope containing the main collection lens and the opposite end of the microscope containing the left and right ocular tubes.
With the advent of modern vitreoretinal surgical procedures, including vitrectomy, retinal membrane removal and subretinal blood and membrane removal, the need to visualize a wide field section of the fundus, including the far peripheral retina, has become increasingly important. To this end, a variety of indirect ophthalmoscopy lens systems, both contact and non-contact, have been utilized or specially developed by researchers and manufacturers to assist the physician and to advance the state of the art.
Although providing a wide field of view required for present day vitreoretinal surgical procedures, an inherent disadvantage of these indirect ophthalmoscopy systems lies in the fact that the produced aerial image, of both the retina, and as importantly, the surgical instrumentation introduced into the eye, is reversed and inverted. Without an image inverting and reversing system, the physician may find it difficult, if not impossible, to perform a surgical procedure while viewing the surgical instrumentation and their movements within the eye in a vertically and horizontally reversed orientation.